Unusual conditional formatting problem in Calc

I am using version 4.4.1.2 with Linux Mint. I have constructed a Stock Quote spreadsheet using getyahoo for the quotes. I entered the formatting for the stock price change cell which should have resulted in either a red or green background with white letters. Instead I get the usual clear cell with the price change in black letters. I have tried both Style Formatting as well as Conditional formatting and all seem to enter properly, but the resulting formatting never appears. Even wackier is that if I add another cell into the spreadsheet with the exact same formula and formatting it works properly but only if I also keep the non-working cell in the spreadsheet. Hitting the Recalcualte Hard button makes the original cell work properly. Is this a bug or am I just buggy? Please help.
Thanks